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Abstract: The gadolinium iron garnet (GdIG, Gd3Fe5O12) and yttrium iron garnet (YIG, Y3Fe5O12), and their GdIG X :YIG1− X composites, were obtained by a new solid-state procedure. The microstructure of the samples was studied by X-ray powder diffraction and Rietveld refinement, Vickers microhardness and scanning electron microscopy. The density and microhardness behavior were studied as a function of the lattice parameters for the composite samples. In the present work, the magnetic and dielectric properties of the GdIG X :YIG1− X composite at radio and microwave frequencies were also studied. The magnetic permeability and dielectric permittivity and loss properties for the composite GdIG X :YIG1− X showed good potential for use in components, when one is looking for moderate ε r′ and μ r′ materials with low loss in the radio-frequency and microwave range. [Copyright &y& Elsevier]

Abstract: Y3Fe5O12 (YIG) crystal has many attractive characteristics, such as low dielectric loss, narrow resonance linewidth in microwave region and also possesses a good saturated magnetization value. Composite technology in general sets out to combine materials in such a way that the properties of the composite are the optimum for a particular application. The different materials work together to give a composite of unique properties. In this work, we present the preparation procedure (obtaining) of the GdIG X :YIG1− X ferrimagnetic ceramic matrix composite by mechanical alloying and calcinations. Besides that, we study its properties by X-ray powder diffraction, infrared, Micro-Raman, 57Fe Mössbauer spectroscopy and hysteresis loop measurements. [Copyright &y& Elsevier]

Abstract: In this work, we report electrical measurements of CaCu3Ti4O12 (CCTO) and (BaTiO3–barium titanate, BTO) thick films. The dielectric constant (K) measurements shows that the BTO thick film present a higher K compared to CCTO compound, in the range of frequencies under study. However, for the composite film (CCTO50 and CCTO50T films), one has an unexpected result; the dielectric constant is higher for all the frequencies under study. The BTO–CCTO composite films do not obey the empirical mixing rule. These electric properties were also studied in the temperature range of 80–300K. For the CCTO film, two relaxation processes were detected. The calculated activation energy was around 0.51eV for temperatures above 200K. One second relaxation process was observed on cooling below 200K with activation energy around 0.061eV. For the composite film CCTO50T, both relaxation processes are still present. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These films are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones, for example), where the miniaturization of the devices is crucial. [Copyright &y& Elsevier]

In this paper, we will study the effect of the presence of CCTO (CaCu3Ti4O12) in the dielectric permittivity and loss of barium titanate (BTO-BaTiO3) thick films. These films were prepared in two layers geometry using the screen printing technique on Al2O3 substrates. Mechanical alloying followed by the solid state procedure has been used successfully to produce powders of CCTO (CaCu3Ti4O12) used in the films. We also look at the effect of the grain size of the BTO and CCTO in the final properties of the film. These samples were studied using X-ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopies. We also did a study of the dielectric permittivity (K) and loss (D) in the medium-frequency (MF) range (100 Hz–1 MHz), of the films. The role played by firing process in the film preparation and the crystallite size of CCTO and BTO in the dielectric constant and structural properties of the films are discussed. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These films are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones, for example), where the miniaturization of the devices is crucial. [Copyright &y& Elsevier]

Abstract: Na[Ru(SO3)(TCNQ)(bpy)2] and [Ru(SO3)(bpy)2(TCNE)] complexes were synthesized and characterized by means of electrochemical techniques and electronic, vibrational and electron paramagnetic resonance (EPR) spectroscopies. Vibrational data indicated a metallocyclopropane configuration for TCNE while TCNQ ligand is coordinated through the nitrile fragment. EPR data indicated the reduced state for the metal centers and for the TCNQ ligand (TCNQ−). The values of the potentials assigned to the redox processes associated to the TCNX ligands indicated a decrease in the electron transfer barrier. Data of dielectric measurements hinted that TCNQ containing complex is more polarized than the TCNE containing compound. Impedance spectroscopy measurements indicated a temperature-dependent relaxation process for both the complexes. However, for TCNQ containing complex, the results suggested the transition from long-range to short-range mobility. In addition, two values of activation energy (2.0 and 0.6eV) were calculated for this complex suggesting a phase transition process. [Copyright &y& Elsevier]